Tread block core for endless tracks and the like



"Ouch 12,1943. Rfl. scHoNlTzER E-rm. 2,331,350

TRD BLOCK" com Fen ENDLEss TRACKS AND THE LIKE l Filed Jan'. 1s, 1942 s sheets-sheet 1 'ih/.f J y f '/NvENToRs:

Ruvo/.PH I. SCHON/T251?,

EDWIN L. ALLEN FG 4' HARO/.o B. MugTE/-e @Y u wmf/W ATTORNEYS 06912, l943- R. l. scHoNn'zER Erm. 2,331,350

TBEAD BLOCKYCORE FOR ENDLESS TRACKS AND THE LIKE Filed Jan. 1s, 1942 s sheets-sheet 2 /Nvz-:Nros: HuoovLP/f I. SCHON/775,4 EDw/N L. ALLEN B HARoLo B. Musv-ER A-rraRNEYs.

06h12,' vT943- R. Al'. scHoNl'rzR ETAL r 2,331,350.A y

TREAD BLOCK-,conm Fon ENDLEss TRACKS -AND THE LIKE EDw//v L. ALLEN HAROLD MUSTER Oct. 12, 1943. R. l. scHoNlTzER ETAL l 2,331,350

I TREAD BLOCK CORE FOR ENDLESS 'TRACKS AND THE' LIKE l Filed Jan. 16, 1942 @Sheets-Sheet 6 RUDOLPH I. ScHoN/Tzf/r E'ow/N l.. ALLEN HARO/ D .15.A Nfl/.STER

BY www# A 1.' 'ron/v: Ys.

vinclusive made in one piece:

Patented Oct. 12, 1943 wie@ 'ramp BLOCK Goan FOR SENDLEss TRACKS V j H AND THE LIKE Rudolph I. Schonitzer, Shaker Heights, and `EdwinL. Allen and Harold B. Muster, Cleveland Heights, Ohio.; said Allen and vsaid Muster as-;

signers to said Schonitzer Application January 16, 1942, Serial No. 426,948

17 claims. (o1. 305-10) y This invention relates to endless tracks for 'vehicles such as tanks, tractors and the like. More particularly, the present invention relates to improvements'in the rea-enforcing cores for the rubber tread blocks of such tracks. q

The type of tread block core withwhich the present invention is concerned is one having generally cylindrical passageways adjacent, and substantially parallel with, the front and rear'edges thereof for the extensionV therethrough of cross rods by means of which a lset of tread blocks, containing cores of the character here involved, Inay be connected (to form an endless track, the laterally projecting ends of such cross rods being suitably connected in pairs, at each side of the track, by means not here necessary to be described.

The present invention has for its general ob'- ject the provision of simple and inexpensive sheet metal cores for tread blocks of the aforesaid type, the construction of said cores being such that they are particularly well adapted for their intended function. y

'A further object of the present invention is the provision, of sheet metal cores having passager ways along their front and rear edges for the reception ofthe track cross rods, the rearportion of therear passageway and the front portion of f the front passageway being of continuous unbroken form, a feature which is of material importance in enabling said cores to effectively withstand the track pull stresses to are subjected in use.

Other objects of the' present invention will be which they hereinafter referredto in connection with the v following description of several tread block cores embodying Vsuch invention, said cores being illustrated in the accompanying drawings, in which Fig. 1 is a side'elevational view of atreadblock core embodying one form of the present invention, the' outer peripheries of the two'layersof V,rubber which are bonded to opposite faces of said indicated in dotlblock containingthe core of Figs. 1 ancl2, the

plane of such view being on the line if-3, Fig. 2;

Fig. 4 is a view similar to Fig. 1, with the twopiece inner member of the core ofFigs. l to 3 fing. 5 is a tcp pian View of a. sughuynodined form` of core,` a portion thereof being broken away to show interior constructiomand the projecting front and rear edge portionsv of the two layers of rubber which are bonded to opposite faces of said core to Fform a tread block being indicated in dot-dash lines;

Fig. 6 is a frontelevati'onal view of the core of Fig. 5,-.a portion thereof beingbroken away Ato show interior construction, and the outer peripheries of the aforesaid layers of rubber being indicated in dot-dash lines; A

Fig. y"i isa view,y partly in vertical section and partly in side elevation, of a tread block containing the core of Figs. 5 and 6, the view beingfon the line 'l-1',\Fig.`5; A '2 Fig.' 8 isja top plan 'View of aI slightly inod'ed form of core,*the projecting frontand rear edge portions ofthe two layers -of rubber which'a're eries of the aforesaid layers of rubber;

Fig. l0is a view of a tread block containing the `core of Figs.` 8 and 9, the view being partl'yin v'ertical-section and partly in side elevationon' the 11ne|c-'|e1,rig.-8; l i Figi-11'," isla side elevational 'view-'cfa tread block core embodying another formof the present invention, the outer periphery of thelblock of 'rubberin whichsuch core is embedded toforin 'a tread vblockbeing indicated ndot-dash lines;

Fig. 12 isa top plan View of the core of Fig. 1l,

with a portion of one of theU-shaped clips broken away, and showing in dot-dash lines the projecting front and rear edge portions of the aforesaid block ofrubber; y 1 f y Fig-13 is a vertical sectional View of a tread block containing the core of Figs. l1 and 12, the plane of the'view being on the line 13-13, Fig. 11; .K l .L

Fig. 14is -a view similar to Fig. A11 butshowing a slightly modified form of core; f'

Fig. 15 is a top plan view of the core of'Fig. 14, and showing in dot-dash linesv the projecting yfront and rear edge portions of the block o'f'rub- `yber inwhich such core is embedded to form a Fig. 1'7 is a side elevational view cfa rnodified form of tread block core, `the outer peripheries of specific arrangement of parts herein illustrated Y or described, as the invention obviously may take other forms. It also is to be understood that the phraseology or terminology herein employed is for the purpose of description and not of limi-V tation, the scope of the present invention being indicated by the appended claims.

, As is well known, the tread blocks of an end less track may be of the type, as to size and shape, which are transversely disposed in such track, with the length of each such block coincident with the track width; or the tread blocks may be of the type, as to size and shape, which are longitudinally disposed in parallel endless rows, with the blocks of the several rows `connected by the track cross rods toform a track of the desired width. Merely for the purposes of illustration, therefore, the drawings kshow in Figs. 1 to 4 inclusive and in Figs. 11 to 18 inclusive cores of tread blocks of the latter or longitudinally disposed type, and show in Figs. to l0 inclusive cores of tread blocks of the former or transversely disposed type. It is to be understood, however, that the cores of Figs. 1 to 4 inclusive yand Figs. l1 to 18 inclusive may be made, if desired, of such size and shape as to adapt them for use in tread blocks of the trans- V versely disposed type, and that the cores of Figs. 5 to 10 inclusive may bevmade, if desired, of such size and shape as to adapt them for use in tread blocks ofthe longitudinally disposed type YReferring now to that form of core illustrated in Figs. l to 3 inclusive,k for use in a tread block I0 of the longitudinally disposed type, it will be noted that such core comprises simple and inexpensive sheet'metalmembers which are assembled in stacked relation, one above another, there being a pair of outer core membersand a two-piece inner core member. It also will be noted that said core members, like the layers of rubber II and I2 which are suitably' bonded to the outer faces `of the two outer core members to form the tread block I0, are of generally rectangular shape in plan view; that the side edges of said core members coincide with the` side edges of the layers ofrubberV I! and I2; and that the length of the two outer core members is substantially coincident with the length of `said layers of rubber.

For'manufacturing economy and simplicity of assembly, the two outer core members (the -top and bottom core members, as viewed in the drawings) are preferably duplicates, as here shown. Similarly, the two parts of 'the inner core member arerpreferably duplicates, as here shown. i Y

For the reception of the two cross rods (not shown) by means of which the tread block I0 is connected to adjacent tread blocks in an endless track, the two-piece inner core member is constructed lto provide therethrough, at the front and rear edges thereof, a pair of transverse and generally parallel passageways I4 of generally cylindrical form. As here shown, each part of said inner core member is bent back upon itself or reversely bent to provide at the bend a tubular portion I3 (dening a cross rod receiving passageway I4) and a pair of transverse overlappingly related edge flanges of unequal width, the wider edge flange being designated by the reierence numeral I5 and the narrower edge flange being designated by the reference numeral I6. As best shown in Fig. l, the two parts of said inner core member are so assembled that the projecting portions of their wider edge flanges i5 are in overlapping relationship, the result being to space apart the two generally parallel tubular portions I3 thereof by a distance sub stantially equal to the joint width of a wide iiange I5 and a narrow fiange I6.

To securely maintain in overlapping relation the edge flanges I5 and I6 of each part of the inner core member, and to thereby effectively maintain in closed condition the passageway I4 provided by the tubular portion I3 thereof, weld ing is here utilized, the welding being preferably of the well known resistance type. In Fig. 2 is shown the spot welds vII by which are rigidly and securely united the overlapping edge flanges I5 and I6 of each part of said inner core member, there being seven such spot welds spaced in a row along substantially the full length of such flanges and located asclose as possible to the tubular portion I3. As will be readilyunderstood, however, the number and spacing of such spot welds I1 may be varied, as desired.

Welding, preferably of the resistance type, also is here utilized to rigidly maintain in assembled relation the two parts of the inner core member. As shown in Fig. 2, the overlapping portions of the wider edge flanges I5 of said inner core parts are rigidly and securely united by the spot welds I 8, there being seven such spot welds spaced in a row along substantially the full length of such flange portions, although the number and spacing of such spot welds IB obviously may be varied.

As best shown in Fig. l, the two outer core members (which are of duplicate character, as heretofore pointed out) are provided at their front and rear edges with overlapping flanges 20 and adjacent said ilanges, the outer core members are provided with transverse matching corrugations 2| (each of semi-cylindrical form) to receive in nested relation the tubular portions I3 of the inner core parts. For added strength and rigidity, the two generally parallel corrugations 2| of each outer core member are bridged by a centrally disposed rib 22 of channel-shaped cross section, the outer wall 23 of said rib being provided, if desired and as here shown, with a longitudinally disposed channel 24.

To securely maintain the outer core members in assembled relation with the two-part inner core member, welding preferably of the resistance type, is here utilized. In Fig. 2 is shown the spot welds 25 by means of which the front flanges 20 of the outer core members are rigidly and securely united in overlapping relation, and the spot welds 26 by means of which the rear iianges 20 of said outer core members are rigidly and securely united in overlapping relation. Although the number and spacing of the spot welds 25 and 26 obviously may be varied as desired. seven spot welds 25 and a like number of spot welds 26 are here shown, the spacing thereof being such that the front and rear edge ilanges of each outer core member are united to the corresponding edge filanges of the other outer core substantially their :full

lation the front danses 20 of thetwo outer-core members and the spot welds 25 by which are rigidly united in overlapping relation the rear` .flanges 20 of said. outer core members may be supplemented by brazilie to the tubular portions `.I3 of the two-partinner core member thercorru- -eations :2 I oi' said outer core members. Forsuc'h 'brazilie purposes, each of said corrugations is provided with suitable apertures 21 laffording aceess'to the tubular portions I3 of the inner core member and receiving more or less of the brass or shelter 27a utilizedin the brazing operation, Said apertures preferably being located as close as possible to the edge anges 2D, as shown in Figs. land 2. Although the number or aperturesv 2l with which each corrugation 'Mis provided may be such as to enable them to be spaced along the full length of said corrugation, each such corrugation is here provided with Vfour of the apertures 2i, two adjacent each end of said corrugation, as clearly shown in` Fig. 2.

Preferably and as here shown,` those side edge portions 2B of the outer core members which lie on opposite sides of the longitudinally disposed ribs 22 thereof, between the corrugations 2l, are welded to the end edge portions of the voverlapllng Wider flanges I of the inner core parts. In Fig. 2 areshown the'two spot welds 29 by means of which'the edge portions28 at each side of the outer core members are rigidly and rmly united to the overlapping end portions of the flanges l5 of the inner core parts.

VFrom the foregoing description of the tread and as a result, no further description of it, is believed to be necessary. .Y

Although the kCore of Figs. 5 to '7 inclusive is `for a tread block 33 of the transversely disposed type, said core -diier-s but slightly, structurally, from the cores heretofore described. So fiar as the outer members of this core are concerned, they differ structurally from the corresponding members of the coresof Figs. y1 toil inclusive only iny that their bridging ritsen are much wider thanthe corresponding ribs of the outerimem.-

bersA of thecores ofgFigs. 1 to 4 inclusive and in the edge portions of its end flanges 36 and 31 are in overlapping,v rather than in abutting, relationship. As bestshownin Fig. 7, the flange 36 has its edge portion oiTset to overlie the edge portion of theflange 31, the overlapping portions ofthe two flanges being rigidly and securely united by spot welds 38 spaced in a row and extending sub.- stantially the full length of the overlappingfflange portions., as clearly shown in Fig. 5. Preferably, and as here shown, they outer ends of the offset portion of ange 36 are cut away, so` as to enable such offset` ilange portion to lie within therib 34 of the adjacent outer core member, as clearly block core of Figs.l l to'3 inclusive, itwill be evident that said core, of sturdy box-like form. in

.,cross section, is Welladapted for the effective between the front and rear flanges 'rilouf` the .two

outerv core members are bridged by. continuous arcuate sections of the tubular portions I3 o f the Vtwo-part inner corev member. This is. a moet important strueturalfeature of this core, inasmuch as vit eiectively prevents any tendency for the welded flanges 20 of the outer core members "to lseparate due to the track pull stress between the connectedtubular portions I3 of adjacent tread blocks in an endless track. It also will be evident that the spot welds Il and I6 of the inner core Vparts are in shear, rather than in tension, with the result that there is no likelihood of disassembly of the two parts of the inner core member or separation o'f their overlapping flanges l5 and i8. i I s If desired, and as will be readily understood, the twoepiece inner core member of the core of Figs. l. to 3 inclusive may be made in onepece,

as in the core of Fig. 4. As shown in Fig. 4, the

`thereof and singly matches the two end flanges V3l. In all other respects, the core of Fig. 4 is identical with the core of Figs, 1 to 3 inclusive vthe same substantial thickness.

tread block 39 has increased cushioning characshown in Fig. 5. Except for the differences herein pointed out,`thercore of Figs.-5 to?? inclusive is structurally the same asthe cores heretofore described, and no further description of it is believed to be necessary. i

The core of Figs. 8 to 10 inclusive.' for ya tread block 39 of the transversely disposed, type, has

a one-piece inner core member Whichstructurallyk is thez same as the one-piece innercore mem- -zfb`er of Fig. ifalthough there is, ioi course, a difference in the size and shape `vorisuch members.

'As Yto-zthe :two outer members Yof the core of Figs. 8 to 10i inclusive, it will be noted said core mem' bers Vdiffer from the correspondingmembers lof the core of Figs; 5` to'? inclusive in that the `two corrugations du 4offeach outer core member are bridged bytwo laterally spaced'ribs 4l ofY generallysenii-circular cross section. rather than by one wide rib of channels-shaped cro-ss section. As best; shown in'Fig. 9, the two duplicate sheet metal outer members of the core of Figs. 8 to' 10 inclusiva-when assembled on opposite faces of the inner member thereof, have their ribs di in oppositely disposed relationship to thereby form` a pair of generally tubular ribs, and any tendency of said core tobuckle or the like is effectively resisted. v

With such a constructiomthe layers of rubber 42 and 43, which are bonded to opposite faces of thiscore to form the tread block 39, have middle portions 44a and side edge portions 44h of As a result, the

teristics, as will be readily understood.

The core of Figs. l1 to 13 inclusive is for a tread block k45 of the longitudinally disposed type, said core being embedded in a block' or rubber 45 to form such tread block. .As best shown in Fig. 1l, this core comprises a two-part core i member which differs from the two-part inner member of. the core of Figs. 1v to 3 inclusive only than Yits tubular portions 41. To aid rin mainftaining the two parts of said core member in assembled relation, and to give this core increased strength and rigidity, two U-shaped sheet metal clips 48 are utilized, said clips being slipped over the anges of the two parts of said core member from opposite sides thereof and being suitably welded to said flanges as indicated by the spot welds 49 in Fig. 12, there being, for example, 'three such spot welds adjacent the bend of each suchclip and a corresponding number of spot welds adjacent its free ends. The two clips 48, which substantially abut at their inner ends, are of such size and shape as to jointly cover said flanges, and inasmuch as said flanges are of reduced length, the outer bent ends oi said clips are substantially flush with the side edges of the tubular portions 41 ofthe two parts of this core member and substantially flush with the side edges of the rubber block 4E in which such core `parts and such clips are embedded.

As in the cores heretofore described, the front and rear cross rod-receiving passageways 5l) of the tubular portions 41 of the two-part member of the core of Figs. 11 to 13 inclusive are closed at their front and rear, respectively, by continuous core member sections of arcuate form. Similarly, the spot welds Sla by which such core parts are maintained in assembly (six, in the present instance), and the spot welds Sib by which the flanges of each such core part are united in overlapping relation (six, in the present instance), are in shear, rather than in tension. As a result, the'core of Figs. 11 to 13 inclusive, like the cores of Figs. 1 to 10 inclusive, is particularly well `adapted for effective and durable re-enforcement of the'rubber block'46, as will be readily understood. l

If desired, and as will be readily understood, the two part member of the core of Figs. 11 to 13 inclusive may be made in one piece, and the clips 48 replacedby web extensions, as in the core of Figs. 14 to 16 inclusive. As best sho-wn in Fi-g. 16, the web portion 52 of the one-piece member of the core of Figs. 14 to 16 inclusive is provided with a pair-of side extensions 53 which are bent over and suitably welded to the substantially abutting end flanges 54 -of said core member. In Figs. is shown the spot welds 55 by means of which said web extensions are rigidly and securely united to the anges 54, and the spot welds 55 by means of which said anges are rigidly and securely united to the web portion 52. Inasmuch as this core is otherwise the same as the core of Figs. 11 to 13 inclusive, no further description of it is believed to be neces- Sary.

The core of Figs. 11 and 18, for a tread block of the longitudinally disposed type, comprises two duplicate sheet metal core members which differ structurally from the duplicate outer members of the core of Figs. 1 to 3 inclusive in that the top walls 51 of their bridging ribs 58 are not channeled and in that portions 59 of their corrugations 60 are outwardly offset. As best shown in Fig. 1'1, the two pairs of matching corrugations of these two core members provide the two generally parallel passageways necessary for the reception of the track cross rods` heretofore mentioned.

In order to insure against any possible separation of these two core members, at the spot welds 6I by which their front ilanges 62 are rigidly united in overlapping relation and/or at Ythe spot welds 63 by which their rear anges G4 A"are rigidly united in overlapping relation, under the track pull stresses applied through the cross `rods (not shown) in the passageways defined by the two pairs of matching corrugations G0, arcuate sheet metal lining members are provided for portions of such passageways. As best shown in Fig. 1'7, the rear portion of the rear passageway is provided with such a lining member 66 and the front portion of the front passageway is provided with a corresponding lining member 61, said lining members being welded or otherwise rigidly secured to the offset portions 59 of the corrugations 58 and lying in the recesses which are formed thereby. As will be evident from an examination of Fig. 11, the lining members 66 and 61 constitute, in effect, continuations of the non-offset portions of said corrugations in forming within each such pair of matching corrugations a cross rod-receiving passageway of generally cylindrical contour.

In the core of Figs. 17 and 18, as in the cores of Figs. 1 to 10 inclusive, the parting line between the welded front flanges 62 and the parting line between the welded rear flanges 64 are bridged by continuous metal sections of arcuate ,form which so distribute and bear the track pull stresses that there is no likelihood of the separation of the core members by failure of the spot welds 6I and 63 by which their front and rear anges are respectively united.

Further features and advantages of cores embodying the present invention will be readily apparent to those skilled in the art to which the invention relates.

What we claim is:

1. A core for the rubber tread block of an endless track of the type in which the tread blocks of such track have cross rods extending therethrough, said core comprising an inner sheet metal core member having front and rear tubular portions extending along and co-extensive ,with the front and rear ends, respectively, thereing apassageway for the extension of a cross rod therethrough, the front wall portion of said front passageway and the rear wall portion of said rear passageway being of unbroken continuous form, and a pair of outer sheet metal core members rigidly connected with said inner core member and engaging opposite faces thereof.

2. A core for the rubber tread block of an endless track of the type in which the tread blocks of such track have cross rods extending therethrough, said core comprising an inner sheet metal core member having front and rear tubular portions extending along and co-extensive with the front and rear ends, respectively, thereof and connected by rigidly united overlapping portions, each of said tubular portions defining a passageway for the extension of a cross rod therethrough, the front wall portion of said front passageway `and the rear wall portion of said rear passageway being of unbroken continuous form, and a pair of outer sheet metal core members rigidly connected with said inner core member and engaging opposite faces thereof, one of said outer core members being provided with a strengthening rib extending substantially normal to the tubular portions of said inner core member.

3. A core for the rubber tread block of an endless track of the type in which the tread blocks of such track have cross rods extending therethrough, said core comprising an inner sheet core member extending substantially normal to the tubular portions of said two part core member.

11. A core for the rubber tread block of an endless track of the type in which the tread blocks of such track have cross rods extending therethrough, said core comprising a sheet `metal core member having reversely bent front and rear end portions to provide tubular portions at the `bends and a pair of end flanges which 'overlapand are rigidly secured to the middleportion of said core member by which its tubular portions are connected, saidtubular 'portions defining a pair of passageways at the front and rear ends of said core 'member for the extension of cross rods therethrough. I

12. A core for the rubber tread block of an endless track of the type in which the tread blocks of such track have cross rods extending therethrough, said core comprising an inner sheet metal core member having reversely bent front and rear end portions to provide tubular portions at the bends and a pair of end flanges whichoverlap and are rigidly secured to the middle portionof said core member by which its tubular `portions are connected, said tubular portions dening a pair` of passageways at the front and rear ends of saidvcore member for the'extension of cross rods therethrough and a'pair of rigidly united outer sheet metal core members between which said inner core member is disposed, said outer core members being provided with ribs extending between and substantially normal to the tubular portions ofv said inner core member.

13;'A core for the rubber treadblockof yan endless track lof the type in which the tread blocks of such track 1 have cross rods extending therethrough, said core comprising a sheet metal core member having front and rear tubular portions extending along and oo-extensive with'the front andv rear ends,` respectively, thereof and connected by rigidly united overlapping portions inwardlyoiset attheir side edges with respect to the side edges of said tubular portions, each of said tubular portions defining a passageway ,for the extension of a cross rod therethrough, the front wall portion of said front passageway and the rear wall portion of said rear passageway be- ,ing` of unbroken 'continuous form, one of said connecting portions being providedwith side extensions which are bent inwardly to overlap said connecting portions, the vouter ends of said side extensions being substantially ilush with the side edges of saidtubular portions, 14.'A core for the rubber tread block'of an ,endless track of the type inwhich the vtread blocks of such track have cross rods extending therethrough, said core comprising a sheet metal core'member having front and rear tubular portions'extendingalong and co-extensive with the front vand rear ends, respectively, thereof and connected byrigidly united overlapping portions inwardly offset at their side edges with respect to thev side edges'of 'said tubular portions, each of said tubular portions dening a passageway for theextension of a cross rod therethrough, the front wall portionV of said front passageway and the rear wall portion of said rear passageway'being of unbroken continuous form, and a pair of U-shaped sheet metal vclips straddling and rig-V idly united with said connecting portions and extending toward each other from opposite side edges of said connecting portions, the outer ends of said clips being substantially flush with the side edges of said tubular portions.

15. A core for the rubber tread block of an endless track ofthe type in which the tread blocks of'such track `have cross Vrods extending therethrough, said `core comprising a pair of sheet metal core members rigidly connected in stacked relation and provided adjacent their connected front edges with a pair of oppositely extending matching corrugations dening a front passageway, and provided adjacent their connected rear 'edges .with a pairof oppositely extending matching corrugations dening a rear passageway, each of said passageways being adapted to have a cross rod extend therethrough, a sheet metal lining member for the front por- `L0 tion of said front passageway, and a sheet metal lining member for the rear portion oi' said rear passageway, said' front and rear lining members bridging, respectively, the connected iront and rear edges of said core members.

16. A core for the rubber tread block of an endless track of the type in which the tread blocks of such track have cross rods extending therethrough, said core comprising a pair of sheet metal core members rigidly connected in 30 stacked relation and provided adjacent their connected iront edges with a pair of oppositely extending' matching corrugations defining a front passageway and provided adjacent their connected rear edges with a pair of oppositely extending matching corrugations defining a rear passageway, each of said passageways being adapted to have a cross rod extend therethrough,

a sheet metal lining member of arcuate form for the front portion of said iront passageway, and 40 a sheet metal lining member of arcuate form for the rear portion oi said' rear passageway, said front and rear lining members bridging, respectively, the connected front and rear edges of said core members, and said matching projections `being recessed to receive said lining members.

17. A core for the rubber tread block of an endless track of the type in which the tread blocks of such track have ycross rods extending therethrough, said core comprising `a pair of sheet metal core members arranged in stacked relation and having rigidly connected overlapping front edge iianges and rigidly connected overlapping rear end flanges, said core members also being provided adjacent their front edge flanges with a pair of oppositely extending matching corrugations dening a front passageway and being provided adjacent their rear edge flanges with a pair of oppositely extending matching corrugations vdefining a, rear passageway, each `of said passageways being adapted to have a cross rod extend therethrough, a sheet metallining member for the front portion of said front pas- Ysageway, and a sheet metal lining member for the rear portion yof said rear passageway, said front and rear lining members bridging, respectively, the front and rear edge flanges of said core members.

VRUDOLPH r. SCHONITZER.

EDWIN n ALLEN. HAROLD'B. MUSTER. 

